JP-B-3692895 (e.g., FIG. 4) discloses an ink-jet head including a piezoelectric actuator (piezoelectric actuator unit) stacked on one flat surface of a cavity plate that serves as a channel unit in which pressure chambers are opened. On a side surface of the piezoelectric actuator, a side electrode that is used to electrically connect a driving electrode formed on a top surface of the actuator to an external wiring line is formed. According to this configuration, the side electrode may be short-circuited from the metallic cavity plate becomes high. Therefore, in the ink-jet head of JP-B-3692895, the electric short circuit between the side electrode and the cavity plate is prevented by forming a recessed portion in the top surface of the cavity plate, and separating the side electrode the cavity plate from each other with the recessed portion therebetween.
When the ink-jet head described of JP-B-3692895 is manufactured, generally, the piezoelectric actuator is pressed against the top surface of the cavity plate after an adhesive is applied to the top surface of the cavity plate. In that case, a recessed portion formed in the top surface of the cavity plate also functions as a relief groove of the adhesive. That is, the adhesive overflowing from between the cavity plate and the piezoelectric actuator is accommodated in the recessed portion. Therefore, it is possible to prevent poor ejection caused when the adhesive climbs up the side surface of the piezoelectric actuator and adheres to the top surface of the piezoelectric actuator.
However, when the piezoelectric actuator is pressed against the top surface of the cavity plate in manufacturing the ink-jet head of JP-B-3692895, cracks may be generated in a region in the vicinity of an outer edge of the piezoelectric actuator. This is because the region in the vicinity of the outer edge of the piezoelectric actuator that faces the recessed portion is not supported by the cavity plate, and therefore, a pressing force applied to the region in the vicinity of the outer edge acts on the piezoelectric actuator as a shear force. When cracks are generated in the piezoelectric actuator, ink may be ejected poorly or cannot be ejected.